Along the catalytic cracking feedstock becomes heavier and heavier, it is essential for the catalytic cracking catalyst to have both higher activity and higher thermal and hydrothermal stabilities to increase the abilities of heavy conversion and anti-heavy metal contamination. Therefore, it is required that the main active component in the catalytic cracking catalyst, i.e. Y zeolite, has high thermal and hydrothermal stabilities, and remains a suitable contribution of acidic active centers.
The rare earth (RE) modified Y zeolite has relative high thermal and hydrothermal stabilities, and is widely used in the FCC catalyst. However, the sharp rise in the rare earth price results in the remarkable increase in the cost of the FCC catalyst. Therefore, it is desirable to introduce other metal ions to the Y zeolite, to reduce the rare earth content in the Y zeolite and to ensure a hydrothermal stability comparable to the Y zeolite with high rare earth content.
CN1350887A, CN1765492A, and US2007010698A1 propose the preparation methods for metal-modified Y zeolites. However, with comparison to the rare earth modified Y zeolite, the above metal-modified Y zeolites are poor in the thermal and hydrothermal stabilities.
CN101898144A and CN101134576A propose the modification to the framework of Y zeolites to increase the thermal and hydrothermal stabilities of Y zeolites. However, the obtained non-rare earth metal-modified Y zeolites produce a low gasoline yield in the catalytic cracking.